Radio communication system, base station apparatus, terminal apparatus, and radio communication method for radio communication system

ABSTRACT

A radio communication system including: a base station apparatus; and a terminal apparatus, wherein the base station apparatus and terminal apparatus performs radio communication, the base station apparatus includes: a scheduler which divides a radio frequency band used for the radio communication into first and second sub-bands of which respective bandwidths are different, assigns the divided first or second sub-band for transmitting user data to the terminal apparatus or for transmitting the user data from the terminal apparatus, and generates assignment information indicating which of the first or second sub-band is assigned to each terminal apparatus; and a transmitter which transmits the assignment information to the terminal apparatus, and the terminal apparatus includes a receiver which receives the assignment information.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of International Application No.PCT/JP2009/001263, filed on Mar. 23, 2009, now pending, the contents ofwhich are herein wholly incorporated by reference.

TECHNICAL FIELD

The embodiments discussed herein are related to a radio communicationsystem, a base station apparatus, a terminal apparatus, and a radiocommunication method for the radio communication system.

BACKGROUND ART

In an LTE (Long Term Evolution) system, which is one of the nextgeneration mobile communication systems of which specifications arebeing finalized by the 3GPP standardization group and of whichcommercialization is expected in 2010 to 2011 and later, the radiotransmission bandwidth in the downlink direction is divided intosub-bands having a same width (for example, Non-patent Document 1). Userdata for each terminal apparatus is transmitted using one or a pluralityof sub-bands. If user data for a terminal apparatus is assigned to aplurality of sub-bands, these sub-bands are arranged continuously ordiscontinuously on the frequency axis.

In an LTE system, information on association of user data and a sub-bandused for the user data is expressed as a bit map. FIG. 10A illustrates aconfiguration example of a sub-frame, and FIG. 10B is an example of abit map. In the example of FIG. 10A and FIG. 10B, there are tensub-bands in total, and the third and fourth sub-bands from the left(“Y” in FIG. 10A) are used for a terminal apparatus. A bit map isincluded in a control signal, and a resource thereof is assigned to thecontrol channel area of the sub-frame (e.g. “X” in FIG. 10A).

FIG. 11A and FIG. 11B illustrate a relationship between a radiotransmission bandwidth and sub-bands. If the radio transmissionbandwidth becomes wider than the case of FIG. 11A, the total number ofsub-bands increases. If the total number of sub-bands increases, a bitmap length increases, and the information volume of the control signalincreases compared with the case of FIG. 11A. To solve this problem, inthe LTE system, if the radio transmission bandwidth increases, thebandwidth of each sub-band is increased accordingly so that the bit maplength does not increase. FIG. 12A to FIG. 12C illustrate an examplewhen the bandwidth of each sub-band increases as the radio transmissionbandwidth increases, with keeping the bit map length constant.Non-patent Document 1: 3GPP TS36.213V8.3.0

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

However the sizes of user data vary, and if the data volume of user datawhich a base station apparatus or terminal apparatus transmits issufficiently smaller than the size of the sub-band, the utilizationefficiency of the sub-bands drops.

Means for Solving the Problem

According to an aspect of the invention, a radio communication systemincluding: a base station apparatus; and a terminal apparatus, whereinthe base station apparatus and terminal apparatus performs radiocommunication, the base station apparatus includes: a scheduler whichdivides a radio frequency band used for the radio communication intofirst and second sub-bands of which respective bandwidths are different,assigns the divided first or second sub-band for transmitting user datato the terminal apparatus or for transmitting the user data from theterminal apparatus, and generates assignment information indicatingwhich of the first or second sub-band is assigned to each terminalapparatus; and a transmitter which transmits the assignment informationto the terminal apparatus, and the terminal apparatus includes areceiver which receives the assignment information.

Furthermore, according to an aspect of the invention, a base stationapparatus for performing radio communication with a terminal apparatus,the base station apparatus including: a scheduler which divides a radiofrequency band used for the radio communication into first and secondsub-bands of which respective bandwidths are different, assigns thedivided first or second sub-band for transmitting user data to theterminal apparatus or for transmitting the user data from the terminalapparatus, and generates assignment information indicating which of thefirst or second sub-band is assigned to each terminal apparatus; and atransmitter which transmits the assignment information to the terminalapparatus.

Furthermore, according to an aspect of the invention, a terminalapparatus for performing radio communication with a base stationapparatus, the terminal apparatus including: a receiver which receivesan assignment information indicating which of first or second sub-bandis assigned to each terminal apparatus, wherein a radio frequency bandused for the radio communication is divided into the first and secondsub-bands of which respective bandwidths are different, the dividedfirst or second sub-band is assigned for transmitting user data to theterminal apparatus or for transmitting the user data from the terminalapparatus.

Furthermore, according to an aspect of the invention, a radiocommunication method for a radio communication system for performingradio communication between a base station apparatus and a terminalapparatus, the method including: dividing by the base station apparatusa radio frequency band used for the radio communication into first andsecond sub-bands of which respective bandwidths are different, andassigning the divided first or second sub-band for transmitting userdata to the terminal apparatus or for transmitting the user data fromthe terminal apparatus, and generating assignment information indicatingwhich of the first or second sub-band is assigned to each terminalapparatus; transmitting by the base station apparatus the assignmentinformation to the terminal apparatus; and receiving by the terminalapparatus the assignment information.

Effectiveness of the Invention

The present invention can provide a radio communication system, a basestation apparatus, a terminal apparatus, and a radio communicationmethod for the radio communication system which improve the utilizationefficiency of sub-bands. The present invention can also provide a radiocommunication system and the like which prevent an increase in theinformation volume of assignment information on the correspondence of aterminal apparatus and sub-bands to be used by the terminal apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a configuration example of a radio communicationsystem;

FIG. 2 illustrates a configuration example of a base station apparatus;

FIG. 3 illustrates a configuration example of a terminal apparatus;

FIG. 4 is a flow chart depicting an operation example;

FIG. 5A and FIG. 5B illustrate a configuration example of a sub-frame;

FIG. 6A to FIG. 6D illustrate another configuration example of asub-frame;

FIG. 7 illustrates another example of a base station apparatus;

FIG. 8 illustrates another example of a terminal apparatus;

FIG. 9 illustrates another example of a terminal apparatus;

FIG. 10A illustrates a configuration example of a sub-frame, and FIG.10B is an example of a bit map;

FIG. 11A and FIG. 11B illustrate an example of a relationship of a radiotransmission bandwidth and sub-bands; and

FIG. 12A to FIG. 12C illustrate another example of a relationship of aradio transmission bandwidth and sub-bands.

1: radio communication system, 10: base station apparatus, 11: memory,12: scheduler, 13: first multiplexer, 14: second multiplexer, 15: thirdmultiplexer, 17: radio transmitter, 18: radio receiver, 19: moving speedestimating section; 20: data decoder, 21: transmitter, 30: terminalapparatus, 31: radio receiver, 32: control signal decoder, 33: datadecoder, 34: channel estimating section (moving speed estimatingsection), 35: evaluation section, 36: bit map definition desired signalgenerator, 37: fourth multiplexer, 38: fifth multiplexer, 39: radiotransmitter, 40: moving speed estimating section, 41: memory, 42:receiver.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will now be described.

First Embodiment

A first embodiment will be described. FIG. 1 illustrates a configurationexample of a radio communication system 1. In the radio communicationsystem 1 which performs radio communication between a base stationapparatus and a terminal apparatus, the base station apparatus 10includes: a scheduler 12 which divides a radio frequency band used forthe radio communication into first sub-band and second sub-band of whichrespective bandwidths are different, assigns the divide first or secondsub-band for transmitting the user data to the terminal apparatus 30 orfor transmitting the user data from the terminal apparatus 30, andgenerates assignment information indicating which one of the first andthe second sub-bands is assigned to each terminal apparatus 30; and atransmitter 21 which transmits the assignment information to theterminal apparatus 30, and the terminal apparatus 30 includes a receiver42 which receives the assignment information. Each processing of thebase station apparatus 10 and the terminal apparatus 30 is performed,for example, by a processor executing a program stored in a memory.

The scheduler 12 of the base station apparatus 10 assigns each sub-band,divided the radio frequency band into the first sub-band and the secondsub-band of which respective bandwidths are different, for transmittinguser data to the terminal apparatus 30, or transmitting user data fromthe terminal apparatus 30. And, the scheduler 12 generates theassignment information indicating which one of the first and secondsub-band is assigned for transmitting the user data. The transmitter 21transmits the assignment information to the terminal apparatus 30.

The terminal apparatus 30 receives the assignment informationtransmitted from the base station apparatus 10.

Since the respective bandwidths of the first sub-band and the secondsub-band assigned for transmitting user data are different, cases whenthe data volume of the user data becomes sufficiently smaller than thebandwidths of the first or the second sub-band decreases compared withthe cases when the bandwidths of the sub-bands are constant. As aconsequence, the radio communication system 1 of the present embodimentcan increase the utilization efficiency of the sub-bands.

Even if the base station apparatus 10 and the terminal apparatus 30 usesub-bands of which bandwidths are different, the information volume ofthe assignment information is unchanged unless the total number ofsub-bands is changed. Therefore the radio communication system 1 of thepresent embodiment can prevent an increase of the information volume ofthe assignment information.

Second Embodiment

FIG. 2 illustrates a configuration example of the base station apparatus(hereafter “base station”) 10 in the radio communication system 1. Thebase station 10 include a memory 11, a scheduler 12, first multiplexer13, second multiplexer 14, third multiplexer 15, a modulator 16, a radiotransmitter 17, a radio receiver 18, a moving speed estimating section19, and a data decoder 20.

The transmitter 21 in the first embodiment (see FIG. 1) corresponds tothe first to third multiplexers 13 to 15, the modulator 16, and theradio transmitter 17, for example.

The memory 11 stores sub-band bit map definition information (hereafter“bit map definition information”). The bit map definition information isinformation on which a sub-band, out of one or plurality of sub-bands,is used to transmit or receive user data for each terminal apparatus 30(or assignment information). The sub-band is a minimum frequency bandwhich is assigned to transmit or receive user data to/from a terminal30, out of the transmission bandwidth of the radio communication system1. The sub-band includes one or a plurality of sub-carriers. The bit mapdefinition information will be described in detail later.

The scheduler 12 generates a sub-frame (or scheduling information), toindicate which time domain and which frequency band is used to transmitand receive data, for each terminal apparatus (hereafter “terminal”) 30,and outputs it to the third multiplexer 15. There are two types ofsub-frames: a sub-frame in the downlink direction for transmitting datafrom the base station 10 to the terminal 30; and a sub-frame in theuplink direction for transmitting data from the terminal 30 to the basestation 10.

The scheduler 12 generates a control signal for each terminal 30, andoutputs it to the first multiplexer 13. The control signal includes anindividual control information including data modulation information,HARQ information, and bit map definition information. For the bit mapdefinition information, the scheduler 12 reads the bit map definitioninformation stored in the memory 11, and includes it in a read controlsignal. The bit map definition information may be multiplexed in thecorresponding user data. In this case, the scheduler 12 outputs the bitmap definition information to the second multiplexer 14, and the secondmultiplexer 14 multiplexes the bit map definition information with userdata.

The first multiplexer 13 multiplexes each control signal which is outputfrom the scheduler 12.

The second multiplexer 14 multiplexes user data for each terminal 30.Each user data is transmitted from a host apparatus (or host layer), forexample.

The third multiplexer 15 multiplexes information on a sub-frame from thescheduler 12, a control signal which is output from the firstmultiplexer 13, and data which is output from the second multiplexer 14.

The modulator 16 modulates data which is output from the thirdmultiplexer 15.

The radio transmitter 17 performs processing to assign data which isoutput from the modulator 16 to a predetermined frequency band and timedomain based on the information on the sub-frame, and converts thesignal after processing into a radio signal, and outputs the radiosignal. The radio signal is transmitted to the terminal 30 via thetransmitting antenna.

The radio receiver 18 converts the radio signal from the terminal 30,received via the receiving antenna, into a signal before modulation.

The moving speed estimating section 19 estimates the moving speed of theterminal 30 based on the signal which is output from the radio receiver18. For example, the moving speed estimating section 19 estimates themoving speed based on the phase change of a pilot signal, which istransmitted from the terminal 30. The moving speed estimating section 19outputs the estimated moving speed information to the scheduler 12.

The data decoder 20 decodes data from signals which are output from theradio receiver 18. The data decoder 20 outputs a bit map definitiondesired signal (hereafter “bit map desired signal”) transmitted from theterminal 30 to the scheduler 12, and outputs the user data to the hostlayer. The bit map desired signal is a signal transmitted from theterminal 30 when [user accessing] the terminal 30 wants to change thebit map definition information transmitted to the terminal 30, forexample. The details will be described later.

FIG. 3 illustrates a configuration example of the terminal 30. Theterminal 30 includes a radio receiver 31, a control signal decoder 32, adata decoder 33, a channel estimating section 34, an evaluation section35, a bit map definition desired signal generator (hereafter “desiredsignal generator”) 36, fourth multiplexer 37, fifth multiplexer 38 and aradio transmitter 39.

The receiver 42 in the first embodiment (see FIG. 1) corresponds to theradio receiver 31, the control signal decoder 32 and the data decoder33, for example.

The radio receiver 31 receives radio signals transmitted from the basestation 10 via the receiving antenna.

The control signal decoder 32 decodes a control signal for a signal fromthe radio receiver 31. Based on the bit map definition informationincluded in the control signal, the control signal decoder 32 outputssub-band information, which indicates a sub-band assigned to theterminal 30, to the data decoder 33. The control signal decoder 32outputs the modulation method and encoding ratio information included inthe control signal to the data decoder 33.

The data decoder 33 extracts the user data addressed to the terminal 30out of the signal from the radio receiver 31, based on the sub-bandinformation, and demodulates and decodes the user data based on themodulation information and encoding ratio information respectively. Thedecoded user data is output to other processing units of the terminal30.

If the bit map definition information is included in the user data, thedata decoder 33 may extract the bit map definition information out ofthe decoded user data, and output the bit map definition information tothe control signal decoder 32. In this case, the control signal decoder32 outputs the sub-band information based on the bit map definitioninformation, which is output from the data decoder 33.

The channel estimating section 34 estimates the channel required fordemodulating the receive signals, and measures the quality of thedownlink radio line, based on the pilot signal transmitted from the basestation 10.

The evaluation section 35 determines whether the bit map definitioninformation is changed or not based on the result of the downlink radioline quality measurement, and if the bit map definition information ischanged, the evaluation section 35 outputs the notice thereof to thedesired signal generator 36. The evaluation section 35 notifies thechange when the estimation result is lower than a threshold, forexample.

When the notice on the change is received from the evaluation section35, the desired signal generator 36 generates a bit map definitiondesired signal for requesting to change the bit map definitioninformation.

The fourth multiplexer 37 multiplexes user data and a bit map definitiondesired signal which is output from the desired signal generator 36.

The fifth multiplexer 38 multiplexes a control signal and an outputsignal which is output from the fourth multiplexer 37.

The radio transmitter 39 performs such processing as encoding, amplitudecontrol and modulation on an output signal which is output from thefifth multiplexer 38, converts the processed signal into a radio signal,and outputs the radio signal to the transmitting antenna. The radiosignal is transmitted to the base station 10 via the transmittingantenna.

Operation will now be described. Operation in the downlink directionwill be described first.

FIG. 4 is a flow chart depicting an operation example. When theprocessing starts, the scheduler 12 of the base station 10 generates acontrol signal by including initial (default) bit map definitioninformation stored in the memory 11 (S10). The scheduler 12 may outputthe bit map definition information to the second multiplexer 14 so as tobe multiplexed with the user data.

FIG. 5A illustrates a configuration example of a sub-frame, and FIG. 5Bis an example of the bit map definition information. In the presentembodiment, there are different widths in each sub-band assigned to theterminal 30. In the case of the example in FIG. 5A, two sizes ofsub-bands alternately exist in the radio transmission band. Each bitincluded in the bit map information corresponds to each sub-band. Forexample, if the sub-band at the left end in FIG. 5A is assigned for theuser data for a terminal, the bit map definition information becomes“100000”, and if the sub-band second from the left is assigned, the bitmap definition information becomes “010000”. The scheduler 12 createsthe bit map definition information for each terminal 30. In the examplein FIG. 5A, two sizes of sub-bands are arrayed, but all the widths ofthe sub-bands may be different from one another.

In the present embodiment, in the bit map definition information whichis used for specifying a sub-band used for transmitting data for eachterminal 30, the widths of the sub-bands indicated by each bit aredifferent among bits. Or for the sub-bands generated by dividing theradio transmitting band into different bandwidths, the scheduler 12generates assignment information to indicate which sub-band is assignedfor transmitting the user data for the terminal 30.

Due to this, the possibility of assigning a sub-band having a smallerwidth than other sub-bands, when the volume of user data for a terminal30 is smaller than the volume of user data for other terminals,increases, compared with the case when the widths of the sub-bands areconstant. If the volume of the user data is larger than the volume ofuser data for other terminals, a possibility of assigning a sub-bandwider than the other sub-bands increases. Therefore in the case of thepresent embodiment, the utilization efficiency of the sub-band can beincreased compared with a case of using sub-bands having a same width.Even if widths of sub-bands are different, the number of bits in the bitmap definition information remains the same unless the total number ofsub-bands is changed. Therefore according to the present embodiment, anincrease of information volume of bit map definition information can beprevented, and utilization efficiency of the sub-bands can be improved.

Referring back to FIG. 4, the base station 10 notifies the created bitmap definition information to each terminal 30 (S11). The bit mapdefinition information is included in the control signal, or multiplexedwith the user data, and is transmitted to each terminal 30 via the radiotransmitter 17.

Then the base station 10 determines whether or not the data volume is athreshold or less (S12). For example, the scheduler 12 inputs user datato the second multiplexer 14, calculates the volume of the user data perunit time, and determines whether the data volume is the threshold orless by the calculated data volume and threshold. As another example,the data decoder 33 of the terminal 30 calculates the decoded datavolume per unit time, outputs the result to the radio transmitter 39,and the scheduler 12 determines whether or not the data volume is thethreshold or less by the data volume transmitted from the terminal 30.

If the data volume is the threshold or less (YES in S12), the scheduler12 changes the arrangement pattern of the sub-bands (S13). For example,if the data volume of the user data to be transmitted to a terminal 30is much smaller than the size of the initially assigned sub-band, thescheduler 12 changes the arrangement of the sub-bands.

For example, the memory 11 or the scheduler 12 stores a plurality ofsub-frames or sub-band information having the changed arrangement of thesub-bands. The scheduler 12 changes the bit map definition informationby reading sub-frames or sub-band information having an arrangement ofsub-bands that is different from S10. In this case, just like theinitial bit map definition information which is set in S10, the widthsof sub-bands indicated by each bit of the bit map definition informationare different among bits. The scheduler 12 may change the arrangement ofthe sub-bands by changing the total number of sub-bands in the radiotransmission band.

FIG. 6A to FIG. 6D illustrate configuration examples of sub-frames inwhich arrangements of the sub-bands are different from one another. Forexample, the scheduler 12 uses the sub-frame in FIG. 6A as the initialsub-band, and uses the sub-frame in FIG. 6B by the processing in S13.

As a result, if the second sub-band from the left is assigned to aterminal 30 in FIG. 6A, for example, this sub-band is changed to asub-band of which width is smaller than the other sub-bands, as depictedin FIG. 6B. Since the sub-band having a width according to the datavolume is assigned, the utilization efficiency of the sub-bands can beincreased. In the case of using the second sub-band from the left inFIG. 6B for transmitting data in a terminal 30, for example, ifreceiving characteristics deteriorated with the frequency of thissub-band, data can be transmitted using a sub-band having a differentfrequency band by changing the arrangement of the sub-bands (e.g. FIG.6C), hence deterioration of receiving characteristics can be prevented.

The change of the sub-band is transmitted from the scheduler 12 to theterminal 30 via the third multiplexer 15 as the changed sub-frameinformation (or scheduling information). The data decoder 33 of theterminal 30 can decode user data from the base station 10 based on thechanged sub-band information.

Referring back to FIG. 4, when the data volume is the threshold or less(YES in S12), the scheduler 12 determines whether or not a bit mapdefinition desired signal is received from the terminal 30 (S14). Thescheduler 12 determines, for example, whether or not a bit mapdefinition desired signal is input from the data decoder 20.

If a bit map definition desired signal is received from the terminal 30(YES in S14), the scheduler 12 changes the arrangement pattern of thesub-bands (S15). The arrangement pattern can be changed in the samemanner as the processing in S13.

The bit map definition desired signal is generated by the evaluationsection 35 and the bit map definition desired signal generator 36 basedon the result of the channel estimating section 34. If the downlinkradio line quality measurement result is smaller than a threshold, thepropagation path environment is not good, so the evaluation section 35notifies the change so that the width of the sub-band becomes wider thanthe width of the initial sub-band specified by the scheduler 12. Becauseof the change of the arrangement pattern of the sub-bands, the terminal30 has a higher possibility of the width of the changed sub-bandbecoming wider than the width of the initial sub-band. A smaller valuecan more easily be used for an encoding ratio of the transmissionsignals, therefore probability for the terminal 30 to receive receivingsignals having good receiving characteristics increases, and otherreceiving signals can be decoded by error correction based on thesereceiving signals. As a consequence, the terminal 30 can improve thereceiving characteristics.

If the bit map definition desired signal is not received from theterminal 30 (NO in S14), the scheduler 12 determines whether the movingspeed of the terminal 30 is a threshold or less (S16). The scheduler 12determines this based on the moving speed information which is outputfrom the moving speed estimating section 19.

If the moving speed is faster than the threshold (NO in S16), thescheduler 12 changes the bit map definition information (S17). Theprocessing for the change is the same as S13 or S15.

For example, if the moving speed of the terminal 30 is faster than thethreshold (e.g. during high-speed moving), a possibility that thechanged width of the sub-band becomes wider than the initial width ofthe sub-band increases due to the change of the arrangement pattern ofthe sub-bands, and the probability to receive a receiving signal havinggood receiving characteristics increases, just like the case of S15.Therefore the terminal 30 can decode other receive signals using errorcorrection based on this receiving signal, and receiving characteristicscan be improved compared with the case of using sub-bands having a samewidth.

If the moving speed is the threshold or less (YES in S16), on the otherhand, processing moves to S12, and the base station 10 repeats theprocessing in S12 and later.

Now operation in the uplink direction will be described. FIG. 4 is alsoused as a flow chart depicting operation in the uplink direction. Thescheduler 12 reads bit map definition information from the memory 11,and performs scheduling (S10). The bit map definition information isincluded in a control signal, or is multiplexed with user data andtransmitted to the terminal 30. The bit map definition information inthis case is for each sub-band in the radio transmission bandwidth inthe uplink direction (or sub-frame in the uplink direction).

The control signal decoder 32 of the terminal 30 extracts the sub-bandinformation for the uplink direction out of the bit map definitioninformation included in the control signal, and extracts modulationmethod information and encoding ratio information for the uplinkdirection included in the control signal, and outputs them to the radiotransmitter 39 respectively. The radio transmitter 39 performsmodulation and encoding based on this information, and maps the userdata on the frequency axis and time axis, and transmits the mapped userdata.

The evaluation section 35, on the other hand, requests the desiredsignal generator 36 to change the bit map definition information basedon the output result from the channel estimating section 34, and basedon this request, the desired signal generator 36 generates a bit mapdefinition desired signal. The bit map definition desired signal ismultiplexed with the user data, and is transmitted to the base station10.

Depending on whether or not the data volume per unit time in the uplinkdirection, which was decoded by the data decoder 20, is a threshold orless (S12), the scheduler 12 of the base station 10 performs processingto change the bit map definition, that is, processing to change thearrangement of the sub-bands (S13). Just like the case of the downlink,the data volume may be the maximum data volume that the terminal 30 cantransmit. For example, the terminal 30 includes the maximum data volumeof information that can be transmitted in the control signal, and thescheduler 12 of the base station 10 determines whether or not the datavolume per unit time in the uplink direction is the threshold or less.

If the bit map definition desired signal is included in the user datadecoded by the data decoder 20 (YES in S14), the scheduler 12 changesthe arrangement of the sub-bands (S15). The bit map definition desiredsignal is also processed in the same manner as the case of the downlink,and the evaluation section 35 notifies the generation of the desiredsignal based on the estimation result of the channel estimating section34, and this desired signal is generated by the desired signal generator36, and is transmitted to the base station 10.

If the moving speed of the terminal 30 estimated by the moving speedestimating section 19 is faster than a threshold (YES in S16), thescheduler 12 changes the arrangement of the sub-bands (S17). For themoving speed as well, just like the case of the downlink, the movingspeed estimating section 19 of the base station 10 estimates the movingspeed of the terminal 30, and the scheduler 12 can determine whether ornot the moving speed is faster than the threshold by the estimationresult.

The change of arrangement of the sub-bands (S13, S15 and S17) can alsobe performed in the same manner as the downlink direction. After thechange, the changed sub-frame information is transmitted from the basestation 10 to the terminal 30, and the control signal decoder 32 of theterminal 30 outputs the sub-band information to the radio transmittingunit 39 out of the decoded control signal. The radio transmitter 39transmits the user data to the base station 10 via the changed sub-band.

In the configuration example of the sub-frame illustrated in FIG. 5A,the sub-frame specified by the bit map definition information (B0 B1 B2)can represent a sub-frame in the downlink direction, and the sub-framespecified by the bit map definition (B3 B4 B6) can be expressed asrespective sub-frames in the uplink direction.

For the uplink direction as well, according to the present embodiment,the widths of the sub-bands indicated by each bit are different amongthe bits in the bit map definition information which is used forspecifying a sub-band used for transmitting data from each terminal 30.Or the scheduler 12 generates assignment information, to indicate whichsub-band is assigned for transmitting user data from the terminal 30,for the sub-bands generated by dividing the radio transmission band intodifferent bandwidths.

Due to this, if the data volume of the user data which is transmittedfrom the terminal 30 is smaller than the data volume to be transmittedfrom the other terminals, a case may arise where a sub-band having asmaller width than the other sub-bands is assigned, in comparison withthe case of using sub-bands having a predetermined width. Therefore thepresent radio communication system 1 can increase the utilizationefficiency of the sub-bands. Since the scheduler 12 can change thearrangement of the sub-bands having different sizes, instead of fixingthe arrangement, utilization efficiency of the sub-bands can be furtherincreased. In any case, the number of bits of the bit map definitioninformation remains the same, even if the arrangement of the sub-bandsis changed, unless the total number of sub-bands is changed, hence anincrease of information volume of the bit map definition information canbe prevented.

Other Embodiments

Various variant forms can be used to change the arrangement of thesub-bands. For example, the scheduler 12 may change the arrangementpattern of the sub-bands periodically, as illustrated in FIG. 6A to FIG.6D, regardless the processings in S12, S14 and S16. By this change, ifthe data volume of user data for a terminal 30 is smaller than that forthe other terminals, a possibility to assign a sub-band changed to asmaller band than the other sub-bands and improve utilization efficiencyof the sub-bands increases. The change of arrangement of the sub-bandschanges a size of each sub-band indicated by each bit of the bit mapdefinition information, but does not change the number of bits, hencethe information volume is unchanged.

Even in the case of changing the arrangement pattern of the sub-bandsperiodically, the scheduler 12 need not use the four types of sub-framesillustrated in FIG. 6A to FIG. 6D, but may use three types or two typesout of these four types. Also more types of sub-frames may be used.

In the case of changing the bit map definition information (S12, S14 andS16), the scheduler 12 may change the cycle to change the arrangementpattern, such as changing from four types to three types. For example,if the moving speed of the terminal 30 is faster than a threshold, thescheduler 12 changes the bit map definition information using threetypes in FIG. 6A to FIG. 6C out of the four types in FIG. 6A to FIG. 6D.

The scheduler 12 may change the arrangement of the sub-bands so that thetotal number of sub-bands in the transmission band is changedperiodically. In the case of changing the bit map definition information(S12, S14 or S16), the scheduler 12 may change the total number ofsub-bands.

FIG. 7 illustrates another configuration example of the base station 10,and FIG. 8 illustrates that of the terminal 30. FIG. 7 and FIG. 8 areexamples when the terminal 30 includes a moving speed estimating section40.

The moving speed estimating section 40 estimates the moving speed of theterminal 30 based on the phase change of the pilot signals received bythe radio receiver 31. For example, just like the moving speedestimating section 19 of the base station 10, the moving speedestimating section 40 sequentially stores the received pilot signals andstores them for a predetermined period, and then estimates the movingspeed by calculating the phase change of the pilot signals. Theestimated moving speed is multiplexed with the user data by the fourthmultiplexer 37, and is transmitted to the base station 10. The datadecoder 20 of the base station 10 decodes the moving speed, and outputsit to the scheduler 12. If the moving speed is faster than a threshold(YES in S16), the scheduler 12 changes the arrangement pattern of thesub-bands (S17). The scheduler 12 may periodically change thearrangement pattern of the sub-bands (FIG. 6A to FIG. 6D), or may changethe cycle to change the arrangement pattern according to the movingspeed. For example, the scheduler 12 may change the four types ofsub-frames illustrated in FIG. 6A to FIG. 6D, to three types or twotypes of sub-frames according to the moving speed.

The moving speed estimating section 40 may output the estimated movingspeed to the evaluation section 35. In this case, if the moving speed isfaster than a threshold, the evaluation section 35 notifies the changeof the bit map definition information to the bit map definition desiredsignal generator 36. If the bit map definition desired signal isreceived from the terminal 30 (YES in S14), the scheduler 12 changes thearrangement of the sub-bands (S15). Since the moving speed estimatingsection 19 is not in the base station 10, the base station 10 can haveless processing load.

FIG. 9 illustrates another configuration example of the terminal 30. Theterminal 30 includes a memory 41 which stores as terminal capabilityinformation the maximum size of the receivable data (maximum receivabledata volume). The fourth multiplexer 37 multiplexes the user data andthe terminal capability information, and outputs the result. The datadecoder 20 of the base station 10 (FIG. 2) decodes the terminalcapability information, and outputs it to the scheduler 12. If themaximum data volume of the receivable data is a threshold or less (YESin S12), the scheduler 12 performs processing for changing thearrangement of the sub-bands (S13). In this case, the scheduler 12 neednot calculate the data volume per unit time of the user data to betransmitted, and the base station can have less processing load. Theterminal 30 may include the fifth multiplexer 38 output the terminalcapability information, including the terminal capability information inthe control signal, and transmit it.

In the above mentioned example, the arrangement pattern is changed basedon the data volume, bit map definition desired signal and the movingspeed of the terminal 30 (S12 to S17 in FIG. 4). For example, thearrangement pattern may be changed according to the type of the userdata which the base station 10 transmits. The scheduler 12 may input theuser data from a host apparatus, and if the type of the user data isvoice data, FTP (File Transfer Protocol), HTTP data or the like, thearrangement pattern can be changed (S13, S15, S17). For example, thescheduler 12 may determine the type of the user data based on a userdata type information included in the user data, or may determine thetype of the user data by user data type information notified by the hostapparatus. In this case as well, the above mentioned various variantforms can be used. In this example as well, the arrangement of thesub-bands is changed according to the user data volume, henceutilization efficiency of the sub-bands can be improved.

1. A radio communication system comprising: a base station apparatus;and a terminal apparatus, wherein the base station apparatus andterminal apparatus performs radio communication, the base stationapparatus includes: a scheduler which divides a radio frequency bandused for the radio communication into first and second sub-bands ofwhich respective bandwidths are different, assigns the divided first orsecond sub-band for transmitting user data to the terminal apparatus orfor transmitting the user data from the terminal apparatus, andgenerates assignment information indicating which one of the first orsecond sub-band is assigned to each terminal apparatus; and atransmitter which transmits the assignment information to the terminalapparatus, and the terminal apparatus includes a receiver which receivesthe assignment information.
 2. The radio communication system accordingto claim 1, wherein the scheduler changes arrangement of the first andsecond sub-bands in the radio frequency band based on a data volume ofthe user data to the terminal apparatus or a data volume of the userdata from the terminal apparatus, and assigns the changed first orsecond sub-band for transmitting the user data.
 3. The radiocommunication system according to claim 1, wherein the terminalapparatus further includes a transmitter which generates a requestsignal for requesting change of the arrangement of the first and secondsub-bands and transmits the request signal, the base station apparatusfurther includes a receiver which receives the request signal, and thescheduler changes the arrangement of the first and second sub-bands inthe radio frequency band according to the request signal, and assignsthe changed first or second sub-band for transmitting the user data. 4.The radio communication system according to claim 3, wherein theterminal apparatus further includes a channel estimating section whichestimates a channel based on a pilot signal transmitted from the basestation apparatus, and the transmitter of the terminal apparatusgenerates the request signal based on an estimation result output fromthe channel estimation unit.
 5. The radio communication system accordingto claim 1, wherein the scheduler changes the arrangement of the firstand second sub-bands in the radio frequency band based on a moving speedof the terminal apparatus, and assigns the changed first or secondsub-band for transmitting the user data.
 6. The radio communicationsystem according to claim 1, wherein the scheduler changes thearrangement of the first and second sub-bands in the radio frequencyband in every transmitting blocks, and assigns the changed first orsecond sub-band for transmitting the user data.
 7. The radiocommunication system according to claim 6, wherein the scheduler changesthe arrangement of the first and second sub-bands in every transmittingblock at a predetermined cycle.
 8. The radio communication systemaccording to claim 7, wherein the scheduler changes the cycle ofchanging the arrangement of the first and second sub-bands according tothe moving speed of the terminal apparatus.
 9. The radio communicationsystem according to claim 1, wherein the scheduler changes thearrangement of the first and second sub-bands in the radio frequencyband based on a type of data transmitting to the terminal apparatus or atype of data to be transmitted by the terminal apparatus, and assignsthe changed first or second sub-band for transmitting the user data. 10.The radio communication system according to claim 1, wherein thescheduler changes the arrangement of the first and second sub-bands inthe radio frequency band based on a maximum data volume of the user datawhich the terminal apparatus can receive or the terminal apparatus cantransmit, and assigns the changed first or second sub-band fortransmitting the user data.
 11. A base station apparatus for performingradio communication with a terminal apparatus, the base stationapparatus comprising: a scheduler which divides a radio frequency bandused for the radio communication into first and second sub-bands ofwhich respective bandwidths are different, assigns the divided first orsecond sub-band for transmitting user data to the terminal apparatus orfor transmitting the user data from the terminal apparatus, andgenerates assignment information indicating which one of the first orsecond sub-band is assigned to each terminal apparatus; and atransmitter which transmits the assignment information to the terminalapparatus.
 12. A terminal apparatus for performing radio communicationwith a base station apparatus, the terminal apparatus comprising: areceiver which receives an assignment information indicating which oneof first or second sub-band is assigned to each terminal apparatus,wherein a radio frequency band used for the radio communication isdivided into the first and second sub-bands of which respectivebandwidths are different, the divided first or second sub-band isassigned for transmitting user data to the terminal apparatus or fortransmitting the user data from the terminal apparatus.
 13. A radiocommunication method for a radio communication system for performingradio communication between a base station apparatus and a terminalapparatus, the method comprising: dividing by the base station apparatusa radio frequency band used for the radio communication into first andsecond sub-bands of which respective bandwidths are different, andassigning the divided first or second sub-band for transmitting userdata to the terminal apparatus or for transmitting the user data fromthe terminal apparatus, and generating assignment information indicatingwhich one of the first or second sub-band is assigned to each terminalapparatus; transmitting by the base station apparatus the assignmentinformation to the terminal apparatus; and receiving by the terminalapparatus the assignment information.